As far as pricing, it's still cheaper than buying them separately and it gets the indie developers more exposure, which they need. It also somewhat encourages people to pay more than the minimum or buy early and keeps people from paying a penny (which a lot did with the Humble Bundles).

The Humble Bundle already started using a soft version of this pricing model by having it that you get an extra game or games if you pay at least the average at the time of purchase. They just didn't enforce it for the main pack, at least not yet.